"Restricted access to fertility treatment on the NHS, the high cost of private therapy at domestic clinics and a serious shortage of donated eggs are driving couples to visit overseas clinics for help in starting a family. "
...
"IVF patients who need donated eggs are particularly likely to travel. Domestic donors are in short supply because of the removal of anonymity and tough rules against selling eggs.Spain and the Czech Republic are prime destinations, due to laws allowing donors to be paid €900 (£765) and €500 respectively for eggs. British donors get no more than £250 in expenses. "

Now the ban on payment for eggs is being reconsidered:

Pay donors to end the shortage of IVF eggs, says watchdog
"A longstanding ban on selling sperm and eggs should be reconsidered to address a national shortage of donors, the head of the Government’s fertility watchdog says. Payments to donors could cut the number of childless couples travelling abroad for treatment, Lisa Jardine, of the Human Fertilisation and Embryology Authority, told The Times. The removal of anonymity for donors in 2005 and strict rules against payments have provoked a crisis in fertility treatment, forcing many couples to wait years for the therapy they need to start a family. A recent study showed that access to eggs and sperm was the main reason why hundreds of British couples became “fertility tourists” each month."
...
"Her move will raise concerns about a market in human tissue and exploitation of women as egg donation is invasive and involves an element of risk. In countries that allow payment, such as the United States, Spain and Russia, young women often donate to wipe out debts or to fund university fees. Professor Jardine said that the law already treated eggs, sperm and embryos differently from other tissues, so there was no danger of setting a precedent for the sale of organs such as kidneys. Payment would also ensure that more women were treated in licensed domestic clinics, rather than in countries with less stringent regulations. “I’m not saying the decision arrived at before I became chair wasn’t the right one at the time,” she said. “But given the evidence that egg shortage is driving women overseas, I feel a responsibility to look at it again.” "